The main problem with microwave communication is that the curvanture of the earth, mountain and other structure often block the line-of -sight. due to this reason, several repeater stations are normally required for long distance transmission between two points. this problem is overcome by using satellites.
these satellite are launched either by rockets or space shuttles and are precisely positioned it is stationary relative to earth and always stays over the same point on the ground. this allows the gruond station to aim its antenna at a fixed point in the sky. each satellite can receive and retransmit signals.to sightly less then half of the earths surface therefore at least three satellite are needed in geosynchronous orbit to provide world wide data transmission service. hundereds of satellite are now in orbit to handle international and domestic data voice and video communication needs. the JNSAT service of nepal satellites are positioned in outer space in a manner to be accessible from any place in nepal.
to enables a large number of users to benefit from satellite communication it was realized that the size and cost of the receive transmit earth station have to be considerably reduced so that one can easily install a private earth station. to meet this requirements, smaller dish antennas having lower power transmitters and receivers have been built for installation at user's sites.
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